FLOODING

FLOODING

January 10, 2008

Letter addressed to the flood experts at the GRCA. Their reply will be posted.
Hi,
I have been looking at the MTO preferred option for the Hanlon Improvements EA
and I have some concerns re flood issues and alteration of the one zone flood area at the Downey/Kortright/Hanlon intersection. From my understanding from the City of Guelph and attending the PICs it is MTO preferred option to lower Downey Rd. under the Hanlon Expressway. Downey Road is to be lowered to an approximate elevation of 317 ft from its current elevation of 323 ft.

I am aware that the Old Downey Rd. that still exists and was overtopped during Hurricane Hazel. and that the only emergency exit was south on the old Downey Rd.

What is the current status of the existing elevation of the Downey /Kortright intersection with the regional flood. i.e. how many meters is it above/below the 25, 50, 100 year storms and such events as Hurricane Hazel? How many mm or rain and over what period of time would it take for this underpass to be flooded? At what flood elevations will emergency vehicles no longer be able to use the underpass? At how many mm of rain and over what time could this occur?

There was no floodline mapping on the MTO preferred options for the Hanlon at the Dec. 5 PIC #2 I spoke to an MTO rep and he could not tell me where the floodlines were and appeared to unaware of flood potential or the flood spillway in this area.

Has anyone from Stantec or the MTO been in contact with the GRCA re the floodlines and the proposed design of the preferred Hanlon improvements especially the proposed southbound ramp from Downey onto the Hanlon in the one zone floodplain?

I know that as a result of Hurricane Hazel a flood risk map was developed for the Hanlon Creek Watershed in the 1970's or 80's . I have seen this map and it shows what appears to be a major east /west spillway across the Hanlon Expressway down the Hanlon Creek valley to the Speed River through this area and the spillway extends south to where the homes are located in Phase 4 of Kortright Hills. I know that the GRCA allowed some encroachment into the floodplain in the Phase 4 area as well as in the new HCBP.

I walk the area on the east side of the Hanlon and observed the high water mark on the concrete steps and the walkway/storm channel/creek under the Hanlon Expressway and the high water mark was only approximately 6 inches below the walk and this is after only 35mm of rainfall on January 9th. The Stormwater ponds for the HCBP on the east side of the Hanlon were overflowing into the Hanlon Creek. The stormwater pond on the north east side of the Hanlon Creek near the Hanlon Expressway was also overflowing into the creek.

How many mm of rain would have to fall before this conduit would be completely filled and flooding to occur on the east side of the conduit?

How many mm of rain and over what period of time would it take to overtop the Hanlon Expressway and start flooding the west side of the Hanlon Expressway? Was one of the design functions of the Hanlon Expressway in this area to hold back the regional flood?

Was the regional flood even considered in the design of the original Hanlon?

How will the large SWM's to be located in the new HCBP just south of Teal Drive impact the regional flood? Is it possible that Downey Rd. will be flooded just south of Tea because of overflow?

According to the GRCA publication Grand River Conservation Authority Flood Management SystemDate: 07/12/00 "Increasing urbanization and in some regions more intensive agriculture are contributing to increased rates of runoff. The trend and degree of watershed urbanization and other upstream land use changes upstream of a given river location as well as the effectiveness of various remedial measures (storm water practices) need to be taken into account in considering design criteria. For example a recent sub-watershed study in the basin indicated suburban development would increase flood flows by over 50%. Page 23
Over the 10 years there has been a dramatic increase the impervious area in the upper Hanlon Creek Watershed and impervious surfaces that drain into the SWM systems with even more a proposed but not yet approved. What percent impervious currently exists? How much estimated impervious has been approved but not yet built in the Hanlon Creek Subwatershed in the areas east of the Hanlon Expressway and north of Downey Rd?

What are the estimated increased flood flows in the Hanlon Creek Subwatershed as a result of the urbanization of the Watershed?

I would appreciate any information and mapping you may have with respect to my questions and concerns.

Sincerely,

Dr. Dennis Murr

January 10, 2008

To: Contact@guelphhanlon.org

Your suggestion at www.guelphhanlon.org that the culvert that dramatically failed in 9 minutes in Toronto was NEW is not accurate. It in fact was 50 years old and it had not been maintained or modified to handle the changes made related to urban growth and climate change. See "Gathering Storms" attached for details.

The City of Guelph and MTO did implement some state of the art storm water management design at the time of the Hanlon construction in 1972 to protect Hanlon Creek, the highway and the wells. See "Underground Storm Water Management keeping John Galt's town plan alive" attached.

You point out some very real concerns that do need to be addressed. I think it is important however to recognize that the engineers, planners and politicians that we have put our trust in over the years have done a pretty good job of weighing the options and watching out for our community.

I am a 27 year resident of the Shadybrook, Ironwood, Kortright, Woodborough etc. neighbourhood. I am also a concerned grandfather. I will be speaking at Mondays meeting and look forward to learning how we might all work to improve our quality of life in Guelph.

David J. Penny, BES